Skin is subject to insults by many extrinsic and intrinsic factors. Extrinsic factors that can adversely affect the skin include ultraviolet radiation (e.g., from sun exposure), environmental pollution, wind, heat, low humidity, harsh surfactants, abrasives, and the like. Intrinsic factors that lead to skin problems include chronological aging and other biochemical changes from within the skin. Whether extrinsic or intrinsic, these factors result in visible signs of skin aging and damage, such as wrinkling, roughness and histological changes. Moreover, to many people, skin wrinkles are a reminder of the disappearance of youth. As a result, the elimination of wrinkles has become a concern for many people. Anti-wrinkle treatments range from cosmetic creams and moisturizers to various forms of cosmetic surgery.
Extrinsic or intrinsic factors may result in the thinning and general degradation of the skin. For example, as the skin naturally ages, there is a reduction in the cells and the blood vessels that supply the skin. There is also a flattening of the dermal-epidermal junction that results in weaker mechanical resistance of this junction. See, for example, Oikarinen, “The Aging of Skin: Chronoaging Versus Photoaging,” Photodermatol. Photoimmunol. Photomed., vol. 7, pp. 3–4, 1990, which is incorporated by reference herein in its entirety.
Skin contains an elaborate network of elastin fibers that is responsible for maintaining its elastic properties. With excessive exposure to sunlight the elastic fiber system becomes hyperplastic, disorganized and ultimately disrupted. This process is known as actinic elastosis and it is a principal cause of wrinkling, discoloration and laxity of the skin in the exposed areas of the body. As new fibroblasts, endothelial cells and keratinocytes form, the skin can repair itself. However, the skin becomes less able to do so as it ages. Therefore, agents that can accelerate the growth and repair of prematurely aged skin are needed.
Wound healing is also accelerated by increased cellular proliferation and migration of certain cell types. The mechanisms involved in wound healing are often divided into four phases: hemostasis, inflammation, proliferation and maturation. During inflammation, leucocytes accumulate to combat bacteria and the permeability blood vessel walls increases, leading to swelling. If an infection does not develop the number of leucocytes diminishes. Monocytes replace the leukocytes. Macrophages and lymphocytes release growth factors (cytokines) as well as a number of chemical substances, such as histamine, serotonin, and prostaglandins. These substances help regulate the wound healing process. In the proliferation phase, new fibroblasts, endothelial cells and keratinocytes arise, connective tissue is formed, new blood vessels grow and injured tissue is regenerated. Fibroblasts become dominant after about a week, the inflammation decreases and the strength of the tissues around the wound site increases rapidly. During the maturation phase collagen is laid down and scar tissue is formed. This maturation phase might go on for a long time during which time, tissues of various types are regenerated. In order to obtain an optimal healing of skin and associated tissues, the supply of different vitamins and trace elements as well as nutrients should be sufficient as well as the oxygen supply.
While certain skin care compositions are available on the market, such compositions do not effectively stimulate the growth of new skin tissues. Hence, there is a need for formulations that not only improve the appearance but also the health of skin. Ideally, such formulations would provide a range of useful activities such as, for example, wound healing, scar reduction, soothing rashes, eliminating wrinkles and reducing the signs of aging.